Tag Archives: evolution

Dogs have evolved new muscles around the eyes to better communicate with humans. New research comparing the anatomy and behavior of dogs and wolves suggests dogs’ facial anatomy has changed over thousands of years specifically to allow them to better communicate with humans.

In the first detailed analysis comparing the anatomy and behavior of dogs and wolves, researchers found that the facial musculature of both species was similar, except above the eyes. Dogs have a small muscle, which allows them to intensely raise their inner eyebrow, which wolves do not.

The authors suggest that the inner eyebrow raising movement triggers a nurturing response in humans because it makes the dogs’ eyes appear larger, more infant like and also resembles a movement humans produce when they are sad.

The research team, led by comparative psychologist Dr Juliane Kaminski, at the University of Portsmouth, included a team of behavioural and anatomical experts in the UK and USA.

It is published in PNAS (Proceedings of the National Academy of Sciences).

Dr Kaminski said: “The evidence is compelling that dogs developed a muscle to raise the inner eyebrow after they were domesticated from wolves.

“We also studied dogs’ and wolves’ behavior, and when exposed to a human for two minutes, dogs raised their inner eyebrows more and at higher intensities than wolves.

“The findings suggest that expressive eyebrows in dogs may be a result of humans unconscious preferences that influenced selection during domestication. When dogs make the movement, it seems to elicit a strong desire in humans to look after them. This would give dogs, that move their eyebrows more, a selection advantage over others and reinforce the ‘puppy dog eyes’ trait for future generations.”

Dr Kaminski’s previous research showed dogs moved their eyebrows significantly more when humans were looking at them compared to when they were not looking at them.

She said: “The AU101 movement is significant in the human-dog bond because it might elicit a caring response from humans but also might create the illusion of human-like communication.”

Lead anatomist Professor Anne Burrows, at Duquesne University, Pittsburgh, USA, co-author of the paper, said: “To determine whether this eyebrow movement is a result of evolution, we compared the facial anatomy and behaviour of these two species and found the muscle that allows for the eyebrow raise in dogs was, in wolves, a scant, irregular cluster of fibres.

“The raised inner eyebrow movement in dogs is driven by a muscle which doesn’t consistently exist in their closest living relative, the wolf.

“This is a striking difference for species separated only 33,000 years ago and we think that the remarkably fast facial muscular changes can be directly linked to dogs’ enhanced social interaction with humans.”

Dr Kaminski and co-author, evolutionary psychologist Professor Bridget Waller, also at the University of Portsmouth, previously mapped the facial muscular structure of dogs, naming the movement responsible for a raised inner eyebrow the Action Unit (AU) 101.

Professor Waller said: “This movement makes a dogs’ eyes appear larger, giving them a childlike appearance. It could also mimic the facial movement humans make when they’re sad.

“Our findings show how important faces can be in capturing our attention, and how powerful facial expression can be in social interaction.”

Co-author and anatomist Adam Hartstone-Rose, at North Carolina State University, USA, said: “These muscles are so thin that you can literally see through them – and yet the movement that they allow seems to have such a powerful effect that it appears to have been under substantial evolutionary pressure. It is really remarkable that these simple differences in facial expression may have helped define the relationship between early dogs and humans.”

Co-author Rui Diogo, an anatomist at Howard University, Washington DC, USA, said: “I must admit that I was surprised to see the results myself because the gross anatomy of muscles is normally very slow to change in evolution, and this happened very fast indeed, in just some dozens of thousands of years.”

Soft tissue, including muscle, doesn’t tend to survive in the fossil record, making the study of this type of evolution harder.

The only dog species in the study that did not have the muscle was the Siberian husky, which is among more ancient dog breeds.

An alternative reason for the human-dog bond could be that humans have a preference for other individuals which have whites in the eye and that intense AU 101 movements exposes the white part of the dogs eyes.

It is not known why or precisely when humans first brought wolves in from the cold and the evolution from wolf to dog began, but this research helps us understand some of the likely mechanisms underlying dog domestication.

Yet more research on how dogs’ brains work. This time from a research team at E​ötvös Loránd University in Hungary and published in the journal Current Biology.

Using functional MRI, the team could see where blood flowed in the brains of a group of 11 dogs. The dogs had been specially trained using positive reinforcement techniques to lie still in the MRI scanner for six minutes.

A dog lies still in the fMRI scanner, wearing earphones to pipe in sounds as part of the study. (Photo by Eniko Kubinyi)

The team played each dog a series of over 200 sounds across several MRI sessions. The sounds included human voices, dog vocalizations, and meaningless noises.

When the results were compared, it showed that the dogs’ brains appear to have a dedicated area that displays more activity in response to voices (whether human speech or dogs barking) than other meaningless noises (such as glass breaking).

More importantly, that part of the brain shows more activity upon hearing an emotionally positive sound, as compared to a negative one. This means that our dogs are able to distinguish a tone of voice that is positive from one that is negative. (Something many of us probably already knew)

The voice areas of the dogs’ brains is similar to that found in humans, suggesting that our species evolved from a common ancestor almost 100 million years ago, enabling a high degree of communication and social structure.

“We know that dogs don’t have language, per se, but we see now that dogs have very similar mechanisms to process social information as humans,” Attila Andics, lead researcher on the study says. “It makes us wonder what aspects of so-called ‘language skills’ are not so human-specific after all, but are also there in other species. That’s something we plan to look at.”

In a new study published in the journal Molecular Biology and Evolution, author Dong-Dong Wu, et. al., explored the genetic basis of high-altitude adaptation of Tibetan Mastiffs, which were originally domesticated from the Chinese native dogs of the plains.

The authors examined genome-wide mutations (called single nucleotide polymorphisms, or SNPs) of 32 Tibetan Mastiffs, and compared them to 20 Chinese native dogs and 14 grey wolves. Overall, they identified more than 120,000 SNPs, and in their analysis, narrowed these down to 16 genes that have undergone positive selection in mastiffs, with 12 of these relevant to high altitude adaption.

These candidate genes have been shown to be involved in energy production critical to high-altitude survival under low oxygen conditions.

If you have ever watched your dog swim, you’ve probably noticed that intense look of concentration on their face. Research has confirmed that swimming doesn’t come as naturally as, say, walking, running or trotting on land.

Photo by the Society for Integrative and Comparative Biology

Dr. Frank Fish, a professor of biology at West Chester University, set out with his colleagues to understand how real dogs perform the dog paddle.

Dr Fish found a large horse rehabilitation pool for filming eight dogs of six different breeds during swimming. Dr Fish’s own dog was one of the study subjects.

The team analyzed the videos and found that the dogs were swimming with a gait that was similar to a familiar trot on land. When a dog trots, moving at a pace more brisk than a walk, diagonal pairs of legs move together. In swimming, the dog’s legs move in a similar fashion, but even faster than a trot, and the legs move beyond the range of motion for a trot. (This is one reason why I recommend swimming for many – but not all – of my massage and rehab customers.)

Swimming dogs are, essentially, using a basic movement but with some modification. Also, while the movements that make up terrestrial gaits like trotting can vary from one dog breed to another, the dog paddle gait showed very little variation among the different breeds.

Dr Fish says that dogs can be used as a model for precursors to early swimming mammals. He hopes to unravel the steps in evolution that allowed four-legged terrestrial animals to become swimming mammals like the dolphin.

In the meantime, get out there and let your dog swim. For most dogs, it’s great exercise!

A genetic study by Peter Savolainen, a researcher in evolutionary genetics at KTH Royal Institute of Technology in Stockholm, has found that dog breeds from North and South America have Asian ancestry.

The Chihuahua definitely has Mexican heritage

The native breeds have 30 percent or less modern replacement by European dogs. It had been thought, prior to this study, that when Europeans settled in the American continent their dog breeds successively replaced the genetics of the native breeds.

Savolainen’s research group, in cooperation with colleagues in Portugal, compared mitochondrial DNA from Asian and European dogs, ancient American archaeological samples, and American dog breeds, including Chihuahuas, Peruvian hairless dogs and Arctic sled dogs.

They traced the American dogs’ ancestry back to East Asian and Siberian dogs, and also found direct relations between ancient American dogs and modern breeds.

The research confirmed conclusively that the modern day Chihuahua has Mexican roots. The breed shares a DNA type uniquely with Mexican pre-Columbian samples.

The team also analysed stray dogs, confirming them generally to be runaway European dogs; but in Mexico and Bolivia they identified populations with high proportions of indigenous ancestry.

Most dog owners have an opinion about their dog’s intelligence. I regularly hear comments like, “He’s so smart, he’s ahead of the rest of his obedience class” or “He’s not very bright, but we love him.”

When I was working on my management qualification years ago, we were told to go home and ask our partner/flatmate about how they solved problems. Ebony, my Labrador flatmate at the time, came up with these tips, which I thought were very intelligent:

Remember that chasing your tail does not get you anywhere. It also makes you dizzy and less able to focus on the task at hand.

Eat regularly and often. Problem solving is hard work and requires energy.

Don’t underestimate the value of a nap. A problem looks different after you’ve had a good sleep.

If you stare at a problem long enough, it might move on its own.

Don’t be afraid to ask for help. Try looking cute.

If looking cute doesn’t work, try whining.

If whining fails, loud retching noises are guaranteed to get the attention of those around you.

Some problems soften over time. Burying them in the garden hastens this process.

Some problems require more immediate attention. An immediate problem, if left unattended, is likely to result in a much more smelly mess to be cleaned up later.

There are many published works on the subject of dog intelligence. Over the years, I’ve read countless research studies into this subject. There are many institutions involved in the research. All projects have the goal of understanding how dogs think.

Professor Stanley Coren of the University of British Columbia has authored several books about dog intelligence. He states that dogs have the intellectual capacity of a two-year old and can understand more than 150 words.[1]

Researchers at the Max Planck Institute for Evolutionary Anthropology have studied the ability of dogs to interpret human gestures. When researchers hid food beneath one container in a group and pointed to the ‘right’ container, dogs consistently picked up on those cues better than even chimpanzees (a species widely studied because of the evolutionary link between apes and humans).

Earlier this year, a research team at the University of Otago reported on their study that showed that dogs could readily distinguish happy human sounds from sad or angry ones, suggesting an ability to understand human emotions.

Even the dog toy market has recognised that dogs need mental stimulation. The Nina Ottosson range, for example, offers a range of skill level toys designed to make your dog think about how to reveal their food reward.

Daisy demonstrates her intelligence with a Nina Ottosson toy

Despite all of this evidence, including videos of my Daisy using her interactive toys, many of the non-dog people in my life remain unconvinced about the intelligence of dogs. I believe that persistence will pay off. Over time we will see more and more research about the intellectual capacity of our dogs. The non-believers will become believers.